I've been listening to the E9 with DT990/600 and DT880/600 - both are driven to volumes far beyond what I would consider "comfortable", even when the gain setting is on "low". This amp has plenty of power.

This is a very quiet amp. I connected its pre-amp output to my main home theater and turned up the volume on the E9 and my receiver to max, E9 gain set to high, input is provided by USB/E7 from my computer, also with volume set to max. I could hear a very faint hiss that changes according to the volume of the E9 - again, this is with the receiver's master volume set to +10dB. How loud was this? I dragged the volume bar in windows down from max to about 1/10 and let go - the resulting "ding!" hurt my ears.

I will leave listening impressions to others, but so far I've been very happy with it.

I've been listening to the E9 with DT990/600 and DT880/600 - both are driven to volumes far beyond what I would consider "comfortable", even when the gain setting is on "low". This amp has plenty of power.

This is a very quiet amp. I connected its pre-amp output to my main home theater and turned up the volume on the E9 and my receiver to max, E9 gain set to high, input is provided by USB/E7 from my computer, also with volume set to max. I could hear a very faint hiss that changes according to the volume of the E9 - again, this is with the receiver's master volume set to +10dB. How loud was this? I dragged the volume bar in windows down from max to about 1/10 and let go - the resulting "ding!" hurt my ears.

I will leave listening impressions to others, but so far I've been very happy with it.

James from FiiO has indicated that they will offer a package deal of the FiiO E7 and E9. We default to FiiO for pricing information, but given that the E7 sells for $99.90 here in the US, my take is that the pricing on the E7/E9 combo will be very attractive to those who are looking to pick up both.

As for USB signal with the E7 docked, the signal goes from the computer to the back of the E9, then to the dock connector for the E7, gets decoded by the E7, is fed to the E7's dock connector, which goes back into the E9, gets amplified by the E9, and sent out through the headphone output.